The establishment and maintenance of pregnancy requires the coordinate activity of a specialized maternal tissue, the decidua. Extensive investigation from our and other laboratories has established that decidual cells are able to produce hormones and cytokines, and to express steroidogenic enzymes. The overall objective of our research is to understand the involvement of these decidua-derived factors in the maintenance of the proper milieu for fetal development. Gene knockout strategies have revealed a crucial role for prolactin (PRL), Interleukin-11 (IL-11) and for decidual steroidogenic enzymes, 5alpha-reductase type 1 (5alphaR1) and 20a-hydroxysteroid dehydrogenase (20alphaHSD), in the normal progress of pregnancy in rodents. The focus of this grant application is to define the role, regulation and interaction of these decidua-derived factors. The first specific aim centers on the role of decidual-PRL in the inhibition of IL-6 and caspase-3, genes involved in inflammation and cell death respectively. Using both PRL and IL-6 knockouts as well as primary decidual cells and cell lines, we propose to examine whether it is indeed IL-6 expression that leads to fetal death in the PRL (-/-) mice, whether pregnancy can be salvaged by generating double knockout mice for PRL and IL-6, and by preventing IL-6 production in the PRL null mice. We will also determine the molecular mechanism by which PRL silences the decidual expression of the IL-6 gene. Another objective of this specific aim is based on our findings that dPRL acts as a survival factor preventing the expression and activation of the cell death inducer, caspase-3, in the decidua. We will examine the mechanism by which dPRL prevents the activity of this executioner caspase, and determine whether PRL inhibition of caspase 3 is at the transcriptional level and involves the Akt/forkhead pathway. The second aim will focus on the role of decidual IL-11 in the normal progress of pregnancy and more specifically on the reason why IL-11Ralpha gene deletion leads to small decidua and to uncontrolled trophoblast invasion. Finally, in the third aim, we will examine the regulation and the role of decidual steroidogenic enzymes in the maintenance of pregnancy. We will examine the mechanism by which PRL prevents decidual 20alphaHSD expression and whether PGF2a stimulates its expression at the end of pregnancy. We will also examine whether 5alphaR1 is not expressed in the IL-11Ralpha null mice causing high levels of circulating estradiol and precipitating fetal death. We will also test the hypothesis that fetal death in 5alphaReductase type 1 null mice is due to the inhibition of IL-11 signaling in the decidua by high levels of estradiol.